Classification of rice, Milling, Different Milling Technology,Parboiling,Different parboiling Technology

1. RICE
SUBMITTED TO :- A. POONIA
MA`AM
FST 510 :- TECHNOLOGY OF CEREALS
,PULSES AND OILSEEDS
SUBMITTED BY : JAGRITI BHASIN
19412FST008
M.Sc. 1st year, 2nd Semester
DEPARTMENTOF DAIRYSCIENCEANDFOODTECHNOLOGY
FACULTYOF AGRICULTURE
BANARASHINDUUNIVERSITY

2. CONTENTS
 RICE
 CLASSIFICATION OF RICE
 MILLING
 MILLING SYSTEMS
 VILLAGE MILLING
 COMMERCIAL MILLING
 OBJECTIVES OF COMMERCIAL MILLING
 TYPES OF COMMERCIAL MILLING
 GUIDELINES FOR GOOD MILLING
 PARBOILING
 METHODS OF PARBOILING
 ADVANTAGES OF PARBOILING
 DISADVANTAGES OF PARBOILING
 RICE QUALITY
 RESEARCH PAPERS
 REFERENCES

3. RICE
 Rice is the seed of the grass species Oryza sativa (Asian rice) or
Oryza glaberrima (African rice).
 As a cereal grain, it is the most widely consumed staple food for a
large part of the world's human population, especially in Asia.
 It is the agricultural commodity with the third-highest worldwide
production (rice, 741.5 million tonnes in 2014), after sugarcane
(1.9 billion tonnes) and maize (1.0 billion tonnes).
 Rice, a monocot, is normally grown as an annual plant, although
in tropical areas it can survive as a perennial crop.
 Rice cultivation is well-suited to countries and regions with low
labor costs and high rainfall, as it is labor-intensive to cultivate
and requires ample water.

4. CLASSIFICATION OF RICE
 Rice, an annual grass belongs to the genus Oryza.
There are about twenty three species out of which
only two species have been known of their
commercial value being used for cultivation. These
two species are Oryza sativa (Asian rice) and Oryza
glaberrima (African rice).
 The Oryza sativa is the most commonly grown species
through out the world to day while Oryza glaberrima
is grown only in South Africa.
 Of the two, O. sativa is by far the more widely
utilized.

5.  A third form, O. rufipogon , having distinctive partitions spread into South
Asian, China , New Guinean, Australian, and American forms.
 In Asia Oryza sativa is differentiated into three sub-species based on
geographical conditions, viz., indica, japonica and javanica.
 The variety indica refers to the tropical and sub-tropical varieties grown
throughout South and South-East Asia and Southern China.
 The variety japonica is grown in temperate areas of Japan, China and
Korea, while javanica varieties are grown along side of Indicas in Indonesia.

6. MILLING
Milling is a crucial step in post-production of rice. The basic objective of a rice milling system is to
remove the husk and the bran layers, and produce an edible, white rice kernel that is sufficiently
milled and free of impurities.

7. MILLING SYSTEMS
A rice milling system can be a simple one or two step process, or a multi stage process.
 One step milling - husk and bran removal are done in one pass
 Two step process - removing husk and removing bran are done separately
 Multistage milling - can be done in the village or local consumption or commercially for marketing rice; rice
undergoes a number of different processing steps, such as:
1) Pre-cleaning
2) Dehusking or dehulling
3) Paddy separation
4) Whitening or polishing
5) Grading and separation of white rice
6) Mixing
7) Mist polishing
8) Weighing of rice

8.  Village Milling :- Village-type rice mills can be found in rural communities and are used for service
milling paddy of farmers for home consumption.
 Traditional milling : Hand pounding of paddy in a mortar with a pestle is the traditional milling
process in remote villages. Pounding the paddy induces upward and downward forces on grain
against grain that removes the husk and bran layers.
 Commercial Milling :-
 Commercial milling systems mill the paddy in stages, and hence are called multi-stage or multi-
pass rice mills.
 The objective of commercial rice milling is to reduce mechanical stresses and heat buildup in
the grain, thereby minimizing grain breakage and producing uniformly polished grain.
 Compared to village-level systems, the commercial milling system is a more sophisticated
system configured to maximize the process of producing well-milled, whole grains.

9. In modern rice mills, many adjustments (e.g. rubber roll clearance, separator bed
inclination, feed rates) are automated for maximum efficiency and ease of operation.
The whitener-polishers are provided with gauges that sense the current load on the
motor drives which gives an indication of the operating pressure on the grain. This
provides a more objective means of setting milling pressures on the grain.
# Objective of commercial milling
A commercial rice miller will have following objectives:
 Produce edible rice that appeals to the customer - i.e. rice that is sufficiently milled and
free of husks, stones, and other non-grain materials.
 Maximize the total milled rice recovery out of paddy and minimize grain breakage.

10. Types of commercial mills
There are two types of Commercial Mills :-
 Traditional Commercial Mill
 Modern Commercial Mill
 Traditional Commercial Mill :-
Traditional Commercial :- Traditional commercial mills
also consist of different pieces of equipment for the three
stages outlined above. They are often made from wood with
few metal components and are often driven by a single
power source through a system of transmissions. Building
such traditional mills was almost considered an art rather than
engineering.

11. Modern Commercial Mill
Modern rice milling processes consist of:
Stage Function
1. Pre-cleaning removing all impurities and unfilled grains from the paddy.
2. Husking removing the husk from the paddy.
3. Husk aspiration separating the husk from the brown rice/unhusked paddy.
4. Paddy separation separating the unhusked paddy from the brown rice.
5. De-stoning separating small stones from the brown rice.
6. Whitening removing all or part of the bran layer and germ from the brown rice.
7. Polishing improving the appearance of milled rice by removing remaining
bran particles and by polishing the exterior of the milled kernel.
8. Sifting separating small impurities or chips from the milled rice.
9. Length grading separating small and large broken from the head rice.
10. Blending mix head rice with predetermined amount of broken, as required
by the customer.
11. Weighing and bagging preparing milled rice for transport to the customer.

12. Flow diagram of a modern rice mill

13. Guidelines for Good Milling
The best quality rice will be attained if the quality of paddy is good and the rice is milled
properly. To improve the quality of the rice, factors such as the paddy quality and milling
technology should be considered.
To obtain good paddy quality:
• Mill at the right moisture content (MC)
A moisture content of 14% MC is ideal for milling.
If the MC is too low, high grain breakage will occur resulting in low head rice
recovery. Broken grain has only half the market value of head rice. Use a moisture
meter to determine the moisture content. Visual methods are not accurate enough.
• Pre-clean paddy before husking
• Do not mix varieties prior to milling

14. When using milling technology:
1. Use rubber roll technology for husking
Rubber roll huskers produce the best quality. Steel hullers are no longer acceptable in the commercial rice milling
sector, as they lead to low milling recovery and high grain breakage.
2. Use a paddy separator
Separate all paddy from the brown rice before whitening. Paddy separation after husking will lead to better quality
milled rice, and reduce overall wear and tear on the rice mill.
3. Consider two-stage whitening
Having at least two stages in the whitening process (and a separate polisher) will reduce overheating of the grain
and will allow the operator to set individual machine settings for each step. This will ensure higher milling and head
rice recovery.
4. Grade the milled rice
Install a screen sifter to remove small broken and chips from the polished rice. Rice with a large number of small
broken (or brewer’s rice) has a lower market value. The small broken can be utilized to produce rice flour.
5. Monitor and replace spare parts regularly
Turning or replacing rubber rolls, refacing stones, and replacing worn screens regularly will keep milled rice quality
high at all times.

15. Parboiling
 Parboiling involves partial boiling of the paddy before milling in order to increase its nutritional value,
to change the texture of cooked rice, and reduce the breakage in milling.
 The Procedure of Parboiling :-
 The general scheme is to hydrate (steeping) paddy to 32 – 38% moisture and partially gelatinize the
starch by steam heating at 15 lb. pressure for 10 – 20 min.
 Parboiling causes certain physico-chemical changes such as improved milling yields (66–70%),
increased resistance to insects and firmer cooked rice texture accompanied by a darker and more
yellow endosperm.
 Parboiling has further advantages like: during soaking and cooking the water soluble vitamins
(niacin, riboflavin, and thiamine) which are present in germ and pericarp gets migrate into
endosperm and thus improves the nutritional value of parboiled rice.
 Even proteins present on the grain surface are denatured, become insoluble, and therefore are not
removed during washing and cooking.

16. Traditional method of Parboiling Improved Parboiling method of
“CFTRI”

17. Advantages of CFTRI Parboiling Method
 The paddy is soaked in hot water (65-70°C).
 This was developed to avoid bad smell.
 Germ action does not occur in hot water, thus the smell is
avoided.
 Soaking time is reduced to 3-4 hrs.

18. Advantages of Parboiling
 The process imparts a hard texture and a smooth surface finish to the grain as a result which the
breakage in the milled rice is minimized. The reduction in broken rice results in an increase of 3-5 per
cent in the total yield of rice.
 Insects find it more difficult to bite and eat their way through the hard and smooth surface of parboiled
rice.
 The loss of solids in the gruel during cooking is also less in parboiled than in raw rice.
 Milled parboiled rice contains more of B-vitamins than milled raw rice.
 Loss of B-vitamins is less in parboiled rice, during washing and cooking, compared to that in raw rice.
 The cooking quality is different from that of raw rice. Parboiled rice is non-sticky and non-glutinous.
 The parboiled paddy on milling produces a bran higher in oil content (about 25-30 % oil) compared to
raw rice bran (about 10-20 % oil).
 Parboiled rice bran is relatively stabilized compared to raw rice.

19. Disadvantages of parboiling
 It develops a relatively darker colour compared to raw rice.
 The traditional parboiled process produces and undesirable smell.
 Parboiled rice takes more time to cook to the same degree of softness than raw rice.
 Because of long soaking in traditional process, mycotoxins may develop in parboiled rice and
cause health hazards.
 Heat treatment during parboiling destroys some natural antioxidants and hence parboiled
rice develops more rancidity than raw rice during storage.
 Shelled parboiled rice requires more power for polishing.
 Parboiled paddy may choke the polisher because of the higher oil content of the bran.
 Parboiling process requires and additional investment of capital.

20. Rice quality
We could say that:

21. 1.What are the physical characteristics of
grain? (before cooking)
 whole and broken grains.
 shape and size of the grain.
 color of grain.
 Weight.
 damaged and discolored kernels.
 foreign material like dirt, stones.
 moisture content of the grain.
2.What are the chemical characteristics of
grain?
The chemical characteristics are about how the
grain looks after cooking and how it feels when
it is eaten
 gelatinization temperature
 amylase content
 gel consistency
 texture (how it feels when eaten)
 aroma (how it smells)

22. Research Papers
 Effect of cooking methods on nutritional quality of rice (Oryza sativa) varieties
Abstract
The objective of the present investigation was to study the effect of four cooking methods viz. ordinary,
pressure, microwave and solar cooking methods on proximate composition and in vitro protein and starch
digestibility of six rice varieties. The study revealed that after cooking, moisture increased significantly,
whereas, crude protein, fat, ash and crude fibre contents decreased significantly by 1.7 to 4.9, 20.8 to 33.8,
12.7 to 20.0 and 8.2 to 12.2 per cent, respectively under all cooking methods. The in vitro protein and starch
digestibility upon cooking by all methods increased significantly and ranged from 81.87 to 86.60 and 90.60
to 92.14 per cent, respectively. Cooking methods differ significantly.
https://arccjournals.com/uploads/articles/10DR888.pdf

23. PHYSICOCHEMICAL PROPERTIES OF GLUTEN‐FREE PANCAKES FROM
RICE ANDSWEET POTATO FLOURS
ABSTRACT
Gluten‐free pancakes were prepared using rice flour and rice flour replaced with various
amounts, at 10, 20 and 40%, of sweet potato flour. Textural properties of the cooked
pancakes, such as hardness and chewiness generally increased with time after cooking,
whereas they decreased with increased sweet potato flour replacement. On the other
hand, cohesiveness decreased with time, but increased with increased sweet potato flour
in the pancake. Nutritional properties of the rice–sweet potato pancakes, such as protein
content, dietary fiber, total carbohydrate and calories were generally comparable with
those of their wheat counterpart. The only significant difference was in the beta‐carotene
content, which increased from 5.2 to 236.1μg/g when sweet potato flour was
incorporated, from 0 to 40%, into the rice pancake formulation.
https://onlinelibrary.wiley.com/doi/10.1111/j.1745-4557.2005.00059.x

24. REFERENCES
 https://en.wikipedia.org/wiki/Rice
 http://agropedia.iitk.ac.in/content/botanical-classification-rice
 http://www.knowledgebank.irri.org/step-by-step-
production/postharvest/milling#milling-systems
 http://www.knowledgebank.irri.org/step-by-step-
production/postharvest/milling/milling-systems#commercial-milling
 http://www.knowledgebank.irri.org/step-by-step-
production/postharvest/milling/milling-and-quality/item/parboiling
 http://agritech.tnau.ac.in/postharvest/pht_cereal_rice_processing.html
 http://www.knowledgebank.irri.org/ericeproduction/quality_01.html
 https://arccjournals.com/journal/asian-journal-of-dairy-and-food-research/DR-888
 https://onlinelibrary.wiley.com/doi/10.1111/j.1745-4557.2005.00059.x